The present invention relates to a novel process for the efficient and economic production of hythane, an alternative fuel for internal combustion engines. More particularly, the invention relates to a process for the direct conversion of methane to hythane.
The growing regulatory and legislative demands for gradual introduction of pollution-free vehicles in Canada and other industrialized nations of the world have intensified research to find clean burning transportation fuels. Compressed natural gas, methanol and oxygenated fuels are among the leading candidates. Recently, blends of 5-20 vol. % hydrogen and 80-95 vol. % natural gas have been receiving increasing interest. These gaseous mixtures are called "hythane" and have been described by F. E. Lynch et al in U.S. Pat. No. 5,139,002 as having an effective combustion rate similar to that of gasoline, thereby creating a potentially promising substitute for conventional fuels in spark ignition internal combustion engines as well as in compression ignition engines. The pollution emissions from hythane powered vehicles is shown to be well below that of gasoline engines, due to the clean-burning characteristics of the components of hythane (F. E. Lynch and G. J. Egan, Proceedings of the 4th Cdn. Hydrogen Workshop, Nov. 1-2, 1989).
According to the aforementioned U.S. Pat. No. 5,139,002, hythane is produced by blending natural gas and hydrogen in desired proportions. Natural gas is a cheap and abundantly available material. However, this is not the case with hydrogen. At present, hydrogen is principally obtained by an energy- and capital- intensive natural gas steam reforming technology. The process operating under extreme conditions of temperature (&gt;900.degree. C.) and pressure (&gt;20 atmospheres) produces a mixture of H.sub.2, CO and CO.sub.2, having a H.sub.2 /CO ratio of about 3 to 5, and containing typically about 15% CO. The main purpose of steam reforming process is to produce syngas. The production of CO-free hydrogen from such a reactor effluent or product mixture requires either separation of hydrogen by membrane diffusion technology or conversion of CO to CO.sub.2 by a shift conversion process under operating conditions vastly different from the primary steam reforming process. Either of these processes adds substantial cost to the already expensive catalytic steam reforming process. Because of such complexity of the overall manufacturing process, hydrogen is an expansive commodity. As a result, CH.sub.4 --H.sub.2 blends have high prices as well. The situation is further worsened by the requirements of cryogenic storage and transportation of the dangerously reactive hydrogen for mixing with methane or natural gas.